Lapping or polishing



Oct. 5, 1948.

Filed Nov. 6, 1943 C. C. STEVENS LAPPING OR POLISHING 2 Sheets-Sheet 2 /NVE/v ro/a CLA REA/c5 csTfVE/VS,

H/- ATTORNEY Patented Oct. 5, l1948 2,450,742 LAPPING von PoLIsHING Clarence C. Stevens, Forestville, Conn., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application November 6, 1943, Serial No. 509,196

.and comprises all of the features and aspects of novelty herein disclosed. An object of the invention is to produce an improved apparatus and method for lapping or polishing various selected kinds of surfaces on a work piece. Another object is to provide an improved apparatus and method for lapping a spherical or a conical surface of revolution on a diamond or the like. Another object is to provide an improved apparatus for lapping a cylindrical surface or one or more flat surfaces on a work piece with each surface at a selected angle to the Work axis.

To these ends and also to improve generally upon apparatus of this character, the invention consists in the various matters hereinafter described and claimed. In its broader aspects the invention is not necessarily limited to the specific construction selected for illustrative purposes in the accompanying drawings in which Fig. 1 is a plan View of the apparatus. Fig. 2 is a front elevation, some parts being in i section.

locking device.

' A cast iron abrasive disc or lapping Wheel 2 rotates on a vertical axis at an adjustable height and its upper annular flat surface is charged with a fine abrasive such as diamond dust mixed with olive oil. Very minute grooves extending nonradially and non-concentrically resist the tendency of centrifugal force to throw off the charge. y

The diamon-d 4 or other article to be lapped or polished is mounted on the end of a stud secured by a chuck 6 to the end of a normally vertical spindle 8 which has several simultaneous moe tions. The spindle rotates on its axis, is movable 'bodily preferably but not necessarily along a radius of the lapping wheel, and may also be swung around an axis which is preferably parallel tothe lapping surface and to the above mentioned radius. The spindle is driven by a pulley IU whose hub has a downwardly extending sleeve l2 and an upwardly extending sleeve I4, these sleeves being received in the inner race rings of ball bearings I which are preferably of the sealed typeand seated in arms I6 projecting from a floating block I8.` Caps 20 secure the outer race rings of the bearings in the arms. The spindle is splined within the pulley for axial adjustment effected by a screw 22 fastened to the spindle and threaded in a cap 2li on the sleeve lll,

The block i8 is connected to an anchoring block 238 by a pair of parallel reed springs 26 which are secured to the respective blocks by `clamping plates. The block 28 is pivoted on a pivot pin 29 extending between spaced arms 38 which project upwardly from a block 3l fastened to the end of a shaft 32 which is reciprocated lengthwise and rocked on its axis. rThe shaft axis is adjacent to the lapping surface and extends across the latter substantially radially, the shaft axis and the spindle axis intersecting at a right angle. The reed springs allow the spindle and associated parts to float vertically, the weight of them being taken by the lapping wheel and furnishing the lapping pressure which may be supplemented as desired by adding weights or by turning the screw 22 to give the springs an initial flexing, The reed springs are normally horizontal and parallel to the lapping surface or nearly so as indicated in Figs 2 and 4, the block 28 or one of the spring clamping plates then resting on a surface of the block 3.|

between the arms 3l) and being held down by a latch 34 pivoted in a recess of the block 28 and engaging a latch pin 36 towards which it is urged by a spring 38. For convenience in changing the work, the spindle and associated parts may be swung upwardly to a stable position as indicated in Fig. 5, the latch 34 first being swung in off the pin 35. Projections 4U on the block 28 then rest upon the pin 36 and support the assembly.

rEhe shaft 32 is mounted to rock and to reciprocate in bearing boxes 42. A grooved collar 44 is pinned to the end of the shaft and supportsa bracket 4G carrying an electric motor 48 provided with gearing driving a pulley 5@ having a belt 52 extending around and driving the pulley l0. All of the parts connected to the shaft 32 reciprocate and oscillate with it. Reciprocation is imparted by a yoke 54 having pins engaging the grooved collar 4d, the yoke having a pivot at 56 which is adjustable to adjust the stroke of reciprocation. The yoke carries a cam roller engaging a cam groove in a cam 58 secured on ,a rotary shaft 59 driven by a pulley 62 and a belt from a pulley 64.

To oscillate or rock the shaft 32 and thus tilt the spindle back and forth in a plane or planes perpendicular to the lapping surface, the following mechanism is provided. A driving pulley 56 and a belt drive a pulley S8 on a rotary horizontal shaft l0 which is in line with the shaft $9. On the end of shaft 'It is a slotted arm l2 in which a crank pin i4 may' be adjustably secured at any desired distance from the axis. A connecting rod 16 extends upwardly to a long crank arm 18 on a horizontal rock shaft 80 to which is pinned an elongated gear segment 82. The gear teeth engage the teeth on a short gear segment 84 which is pinned to the shaft 32, the mechanism thus oscillating or rocking the shaft and permitting its simultaneous linear reciprocation. The combination of motions is adapted to lap or polish a spherical segment or surface of revolution on the lower portion of the article which may be a diamond for gauging, the radius of the spherical segment being determined by the distance between the upper face of the wheel 2 and the axis of the shaft 32. The spindle 8 intersects the axis of the shaft 32. By holding the spindle against rotation, a cylindrical surface can be lapped. The level of the wheel 2 can be adjusted to determine the radius of the surface as will later appear.

In those instances wherein it is desired to lap or polish a conical surface on the diamond or -other article, the rocking of the shaft 32 is dispensed with and it is locked in a selected angular position which causes the spindle 8 to take a tilted iposition. To this end, the gear segment 84 is locked from oscillation after the oscillating mec-tn anism is disconnected as by removing the ypin 'it 'from the slotted arm 12 or by placing the pin at the axis of rotation. provided at the top with arcuate, stepped surfaces 86 for co-operation with similar surfaces on a locking plate 88 lclamped to a square bar 9i! which is slidable in forks provided by two pairs of spaced guide lugs 92 mounted on the bearing boxes 42. Fig. 2 shows the locking plate E8 in inoperative position and Fig. 4 shows it moved to operative position. The plate 88 has an arcuate slot S4 through which a screw bolt 9S is passed into a hole in the gear segment. The slot 9d is concentric with the stepped surfaces 3G which are arcuate so that the segmental gear and the locking plate will provide for various angular settings of the shaft 32 and of the spindle 8. A scale on the upper edge of the segment measures the angle. When, instead of lapping a conical surface, it is desired to lap a flat surface at a selected angle to the spindle, the spindle rotation is dispensed with as well as its rocking oscillation. Various combinations are procurable as for instance the lapping of a conical surface followed by the lapping of a small radius on the point of the cone.

The lapping or polishing wheel 2 has its spindle journalled for rotation in a quill 98 which is clamped in vertically adjusted position in a split bracket Ulli. The vertical adjustment is effected by a screw m2 abutting against the lower end of the quill and threaded in a base plate. The level of the lapping wheel is thus adjusted to place it at the desired distance from the center cf the shaft 32. To facilitate measurement of this distance, a pin it!! projects from the center of the shaft 32. A pulley 1GB on the wheel spindle is driven by a belt from a pulley Hi8 on the vertical shaft of a motor H9 which has a vertically adjustable slide. This same motor furnishes the power for operating the reciprocating mechanism and the rocking mechanism for the shaft 32. The details are immaterial but a pulley H2 on the motor shaft has a belt driving a pulley l i4 on a vertical shaft, another pulley l l5 on the vertical shaft being belted to a pulley H8 on a shaft projecting from a gear casing 120 which drives the before mentioned pulleys 5t and The gear segment all is ,l

E6. Speeds may be altered by changing pulleys. Without limiting the invention, it may be stated that suitable speeds for polishing diamonds are 108 R. P. M. for the diamond-carrying spindle 8 which the shaft 32 rocks around its axis 20 times per minute and rectprocates axially at 9.92 reciprocations per minute. The lapping wheel rotates at high speed. The machine is readily adapted for grinding operations by substituting a grinding Wheel for the lapping wheel. The term lapping is intended to include abrading and polishing as well as lapping.

I claim:

1. In apparatus of the character indicated, a wheel having a fiat lapping surface, means for rotating the wheel on its axis, a shaft adjacent to the lapping surface and having bearings to hold the shaft parallel to the at lapping surface, a spindle supported by the shaft at an angle which intersects the axis of the shaft, the connection between the shaft and the spindle having means for urging the spindle axially endwise to hold a work piece in yielding contact with the lapping surface, means for rotating the spindle on its axis, means for rocking the shaft on an axis parallel to the lapping surface and extending across it, and means for axially reciprocating the shaft parallel to the lapping surface.

2. In apparatus of the character indicated, a wheel having a fiat lapping surface, means for rotating the wheel on its axis, a shaft adjacent to the lapping surface and parallel thereto, a spindle supported by the shaft at a right angle thereto, the spindle and its support having means to hold a work piece in yielding pressure contact with the lapping surface, means for rotating the spindle cn its axis, and means operable during rotation of the spindle for causing a relative rocking movement between the shaft and the lapping surface on a fixed axis parallel to the lapping surface and extending across it substantially radially.

3. In apparatus of the character indicated, a wheel having a flat lapping surface, means for rotating the wheel on its axis, a spindle having means to hold a work piece in contact with the lapping surface, means for rotating the spindle on its axis, means for moving the rotatable spindle endwise towards or from the lapping surface, and means for causing two relative bodily motions between the spindle and the lapping surface, one motion being that of reciprocation in a direction parallel to the lapping surface and the other motion being a rocking one von a fixed axis which always intersects the axis of rotation of the spindle and lies in a plane spaced from and parallel to the lapping surface.

4. In apparatus of the character indicated, a member having a flat lapping surface, a rotatable spindle mounted for rocking movement around a fixed axis spaced from and parallel to the lapping surface and intersectingthe spindle axis, the spindle and its mounting having means to hold a work piece in yieldable pressure contact with the lapping surface, means for rocking the spindle around said fixed axis, and means for bodily shifting the spindle sidewise in a direction parallel to the axis of rocking to traverse the work piece along the flat lapping surface.'

5. In apparatus of the character indicated, a member having a lapping surface, a pair of blocks, a spindle journalled for rotation in one of the blocks and having means to hold a work piece in contact with the lapping surface, a floating support forthe spindle comprising a pair of parallel springs connecting the blocks and extending substantially parallel to the lapping surface, 'and means for causing relative lapping movement between the work piece and the lapping surface.

6. In apparatus of the character indicated, a member having a lapping surface, a block having a bearing, a. pulley journalled for rotation in the Fbearing, a spindle slidably mounted in thepulley and having means to hold a work piece in contact with the lapping surface, a yielding spring support for the block, and means for sliding the spin- 'dle in the pulley to change the lapping pressure applied by the spring.

7. [In apparatus of the character indicated, a wheel having a at lapping surface, means for rotating the wheel on its axis, a shaft, bearings supporting the shaft to slide axially and rock about a fixed Aaxis parallel to the lapping surface and extending across it substantially radially thereof, a spindle supported by the shaft at an vangle which intersects the axis of the shaft, the connection between the spindle and the shaft having means to hold a work piece in yielding pressure contact with the lapping surface, means for rotating the spindle on its axis, means for rocking the shaft on its fixed axis, and means for causing axial reciprocation of the shaftl in said bearings.

CLARENCE' C. STEVENS.

REFERENCES CITED The following references are of record in the ille of this patent:

Number 6 UNITED STATES PATENTS Name Date Besson et al Sept. 14, 1886 Gilroy Mar. 15, 1887 Hcllely Aug. 7, 1888 Bluntschli Mar. 5, 1889 Armstrong Mar. 10, 1891 Clarke AOct. 18, 1904 Thompson Nov. 15, 1904 Hall Mar. 5, 1907 Hull Dec. 14, 1909 Thiel May 10, 1910 Van Eps June 21, 1910 Wolf et al July 19, 1910 Wallace et al Oct. 29, 1912 Hemming May 26, 1914 Rogers May 25, 1915 Bugbee May 22, 1917 Challet Apr. 9, 1918 Hammon Aug'. 6, 1918 Sanford Dec. 31, 1918 Mantle Aug. 19, 1919 Robertson et al. June 15, 1920 Kalteyer Aug. 5, 1924 Maynard et al. Dec. 23, 1924 Heinz Dec. 30, 1924 George May 22, 1928 Maynard et al July 30, 1929 Carlson Aug. 16, 1932 Spcacci May 31, 1938 Zimmerman Feb. 17, 1942 Hanson Mar. 24, 1942 Houchin Mar. 31, 1942 Pollock Aug. 25, 1942 Simons Oct. 13, 1942 

